The present invention relates to electronic circuits, and more particularly, to modulating the frequency of an RF signal being transmitted
In high-frequency electronic circuits, there is often a need to change the frequency of the transmit signal, i.e., to shift from one frequency to another, in order to prevent interference to and from other RF transceiver units. Such frequency shifting may be achieved by varying the bias to a varactor diode, that in turn, changes the capacitance values disposed in a crystal oscillator circuit.
In other conventional systems, to change the oscillation frequency, a potentiometer is used to vary the resistance of an RC network coupled to the drain terminal of an RF transistor thereby to vary the drain bias voltage. Therefore, the oscillation frequency of the transmit signal can only be varied manually. A need continues to exist for a circuit operative to dynamically vary the oscillation frequency of an RF transmit signal.